Emerson E2 Manuel D’Utilisation

defined Pump Down and Run-Off times will be observed 
as normal.
Electric Defrost

Electric defrost uses electric heaters to defrost the 

evaporator coil. During electric defrost, the application 
will turn the Defrost output ON, which will likewise acti-
vate the heaters connected to the power module’s defrost 
relay.

Any user-defined Pump Down and Run-Off times will 

be observed as normal.

Both the start time and the end time of a defrost cycle 

are determined by the user. The Pump Down, Defrost, and 
Run-Off stages all have fixed durations, and when the last 
stage of the cycle is complete, defrost is terminated.

However, a case controller may be programmed to ter-

minate the Defrost stage of the defrost cycle early if the 
temperature inside the case rises above a fail-safe tempera-
ture setpoint. For certain defrost types, defrost heat may 
also be “pulsed” in order to keep the temperature below 
the setpoint without terminating defrost.
Temperature Termination

One or more temperature sensors in the case circuit 

may be designated as termination temperature sensors. 
The values of these sensors are combined into a single 
control value, and this value is compared to the setpoint. If 
the termination control value is greater than the user-
defined setpoint, defrost will end, and the defrost cycle 
will begin the Run-Off period (if applicable).

Termination sensors may be either analog temperature 

sensors or digital closures (Klixons). Also, Case Circuit 
applications may use the value of the analog case tempera-
ture sensors for use in temperature termination.
Pulsed Defrost

Pulsed Defrost is only available if the circuit is using 

Electric or Hot Gas defrost.

Pulsed Defrost is similar to Temperature Termination, 

except when the termination temperature rises above the 
setpoint, defrost does not terminate. Instead, the output 
that applies defrost heat is turned OFF. The output will 
remain OFF until the temperature falls below the setpoint, 
at which time the output will come back ON.

The Case Circuit application will continue to pulse 

defrost in this manner until the defrost time has passed. 
The defrost cycle will then begin the Run-Off period.

If a case is configured with a demand defrost sensor, a 

case controller may use their inputs as a means of keeping 
scheduled defrost cycles from occurring when frost levels 

are not high enough to require a defrost.

The optical demand defrost sensor may be either an 

analog or digital type sensor. When this sensor detects no 
major build-up of frost, the Case Circuit application 
ignores all scheduled calls for defrost and continues in 
refrigeration mode. When the sensor detects frost, the 
defrost inhibit is cancelled, and the case circuit will enter 
defrost at the next scheduled time.

A demand defrost inhibit only keeps scheduled 

defrosts from occurring. Any manual calls for a defrost 
cycle will occur as normal. CCB demand defrost is cur-
rently not supported in E2. Demand sensors, if present on 
the circuit, will be ignored. 
Demand Fail-Safe Time

To protect against demand defrost sensors that may not 

be working properly, a demand fail-safe time may be set 
up. Demand fail-safe times limit the amount of time a 
defrost inhibit may last. If a demand defrost sensor does 
not detect frost for an amount of time equal to the Demand 
Fail-Safe Time, the defrost inhibit is lifted and the circuit 
will enter defrost at the next scheduled time.

When necessary, a user can initiate an emergency 

defrost cycle from a circuit. Emergency defrost cycles are 
similar to normal defrost cycles, except an emergency 
defrost cycle will ignore all calls for termination and 
remain in defrost for the entire programmed defrost time. 

Emergency defrosts are initiated by the user from the 

Case Control Circuit Bypass screen (see Section 12.6, 
Manual Defrost and Clean Mode).

When a Case Control Circuit application enters defrost 

mode, it sends a message out to all case controllers in the 
circuit to begin defrost at the same time. However, since 
each case in a circuit will have its own termination sen-
sors, it is possible for some cases to terminate defrost 
while defrosts in other cases continue.

When a case controller terminates defrost, it enters a 

state of operation called “the WAIT state.” While in the 
WAIT state, all refrigeration and defrost heat will remain 
OFF. When the Case Control Circuit application detects 
that all case controllers have entered the WAIT state, the 
application will consider the defrost cycle completed, and 
refrigeration will restart.

A case controller manages its anti-sweat heaters by 

monitoring the dewpoint in and around the case area. The 
dewpoint input value is compared to the anti-sweat appli-
cation’s control setpoints (the Full ON setpoint and the